Socket for IC device

ABSTRACT

The present invention is intended to solve the problems by providing a structure comprising a cover, a base frame mounted to the cover via a coil spring, a base frame-fixing frame, boards, through-holes for contact elements, contact elements, printed circuit-fixing pins, and locking means. The locking means have locking lever-fixing shafts extending horizontally. Locking levers are pivotally mounted to the locking lever-fixing shafts, respectively. Kick springs are wound around the locking lever-fixing shafts, respectively. The locking levers have locking lever-pushing portions to form IC device-sandwiching portions. The cover is pushed to cause inner corner portions to push against the locking lever-pushing portions. Each of the contact elements has a contact element center-winding portion and contact element both side-winding portions extending from the contact element center-winding portion. The contact elements are inserted in the contact element through-holes.

TECHNICAL FIELD

The present invention relates to a socket for an IC device and, moreparticularly, to a socket used to connect the contact portions ofnumerous terminals of an IC device with contact portions printed on aprinted circuit board. Especially, the invention relates to a socket fora leadless IC device.

BACKGROUND OF THE INVENTION

In recent years, IC devices have made transition to the leadlesssurface-mount type. For this purpose, IC devices assume a form adaptedfor the surface-mount type. That is, numerous terminal contact portionsare formed without unevenness on the rear surfaces of IC devices.However, it is difficult to make electrical connections by directlymaking the rear surface of an IC device of this kind closely adhered toa printed circuit on a printed circuit board. Hence, a socket isnecessary between the contact portions of the IC device and the contactportions of the printed circuit.

To this end, in the socket structure used for an IC device of this kind,pressure is applied between the contact portions of numerous terminalsformed on the rear surface of the IC device and the printed contactportions on the printed circuit board. Since the connection is completedby the applied pressure force and by the resulting repulsive force, thepressure must be constantly applied, Therefore, the actual situation isthat stable electrical connection cannot be achieved because it isimpossible to apply uniform pressure to many terminals.

Accordingly, it is an object of the present invention to provide asocket which is used for an IC device and which makes electricalconnections between the contact-portions of numerous terminals of aleadless IC device and the printed contact portions on a printed circuitboard easily and reliably, the socket having a cover that is pusheddownward to permit locking levers disposed in four directions to holdthe IC device therebetween reliably in one-touch operation.

DISCLOSURE OF THE INVENTION

The present inventors have conducted investigations earnestly in view ofthe foregoing problem and made a structure comprising: a cover havingopenings in its top and bottom surfaces, respectively; a base framehaving openings in its top and bottom surfaces withdrawably inserted viaa coil spring in the bottom surface of the cover; a base frame-fixingframe for limiting sinking movement of the base frame; boards verticallystacked with the base frame; through-holes for contact elementspenetrating the boards and the base frame; contact elements inserted inthe through-holes for contact elements; fixing pins used for a printedcircuit board and protruding from the bottom surface of the base frame;and locking means mounted between the cover and the base frame. Thelocking means have locking lever-fixing shafts extending horizontallyand mounted at the four sides of the cover and the base frame. Lockinglevers are pivotally mounted to the locking lever-fixing shafts,respectively. Kick springs are wound around the locking lever-fixingshafts, respectively. The kick springs engage the cover and the lockinglevers. Each locking lever has a locking lever-pushing portion and ICdevice-sandwiching portions. The cover is pushed downward to cause innercorner portions to push against the locking lever-pushing portions. Eachcontact element comprises contact element center-winding portionfabricated by closely winding a wire into a coil and contact elementboth side-winding portions extending from the contact elementcenter-winding portion. Each contact element both side-winding portionhas portions closely adhered to both sides of the contact elementcenter-winding portion and a spacing winding portion. The contactelements have both-end portions protruding and inserted into the contactelement through-holes, respectively.

The action of the present invention is as follows. The contact elementseach fabricated by winding a spring wire into a coil are used. Thecontact elements electrically connect the contact portions of numerousterminals of a leadless IC device with the printed contact portions on aprinted circuit board. This assures reliable and stable connections.Further, by depressing the cover of the socket, the locking leversdisposed in four directions are rotated and the IC device-sandwichingportions are released. Thus, the IC device is held between them byreleasing the pressure and electrical connections are made easily.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an embodiment of an IC device socket inaccordance with the present invention;

FIG. 2 is a bottom view of an embodiment of an IC device socket inaccordance with the present invention;

FIG. 3 is a side elevation partially in cross. section of an embodimentof an IC device socket in accordance with the present invention,illustrating a connected state; and

FIG. 4 is a side elevation partially in cross section of an IC devicesocket in accordance with the present invention, illustrating an openstate.

FIG. 5 is an enlarged partial side view of the contact element of the ICdevice socket in accordance with the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention is hereinafter described indetail by referring to the drawings.

The present invention resides in a socket for an IC device. The socketis used to connect the contact portions of numerous terminals of the ICdevice with the printed contact portions on a printed circuit board.Especially, the invention pertains to a socket for a leadless IC device.The socket comprises a boxlike cover 1 having openings in its top andbottom surfaces, a boxlike base frame 2 having openings in its top andbottom surfaces withdrawably inserted via a coil spring in the bottomsurface of the cover, a base frame-fixing frame 2 a for limiting sinkingmovement of the base frame 2, boards 3 vertically stacked with the baseframe 2, a number of through-holes 4 penetrating the boards 3 and thebase frame 2, a number of contact elements 5 inserted in thethrough-holes for contact elements 4, respectively, mounting pins 6protruding downwardly from the base frame 2 and used for mounting to theprinted circuit board, and locking means 7 for the IC device. Thelocking means 7 are mounted between the cover 1 and the base frame 2.The locking means 7 have locking lever rotating shafts 7 a,respectively, in the centers of the four sides of the cover 1 and of thebase frame 2, the shafts 7 a extending horizontally. Locking levers 7 bare pivotally mounted to the locking lever rotating shafts 7 a,respectively. Kick springs 7 c are wound around the rotating shafts 7 a,respectively. Both sides of each kick spring 7 c engage the cover 1described above and the locking levers 7 a. Each locking lever 7 a has alocking lever-pushing portion 7 d. Furthermore, each locking lever 7 ahas an IC device-sandwiching portion 7 e at its front end. The cover 1is pushed downward to cause inner corner portions 1 a to push againstthe locking lever-pushing portions 7 d, respectively. Each of thenumerous contact elements 5 comprises a contact element center-windingportion 5 a fabricated by closely winding a spring wire into a coil andcontact element both side-winding portions 5 b that are closely adheredto both sides of the contact element center-winding portion 5 a andextend from the contact element center-winding portions. Each of thecontact element both side-winding portions 5 b each has spirally woundportions and a spacing winding portion. Each of the numerous contactelements 5 has both-end portions protruding and inserted into thenumerous through-holes for contact elements 4, respectively.

In particular, the IC device socket in accordance with the presentinvention is an IC device socket for electrically connecting the contactportions of numerous terminals of a leadless IC device with the samenumber of printed contact portions in a printed circuit of a printedcircuit board. The cover 1 assumes a boxlike form having openings in itstop and bottom surfaces. The IC device will be inserted into the openingin the top surface later. The base frame 2 (described later) iswithdrawably inserted into the lower opening.

Sufficient space to accommodate locking means 7 (described later) isformed between the base frame 2 and the cover 1. A coil spring (notshown) is interposed between the base frame 2 and the cover 1, and thebase frame 2 is inserted in the lower opening such that its lower sidescan go out of the lower opening. The base frame 2 has openings in itstop and bottom surfaces, respectively. The base frame-fixing frame 2 ais formed under the base frame 2 to prevent the base frame 2 from comingoff the cover 1.

The base frame 2 is centrally provided with a number of through-holesfor the contact elements 4 to penetrate the contact elements 5(described later). Boards 3 are provided with the same number ofthrough-holes 4 for the contact elements as the first-mentionedthrough-holes 4 in the identical positions. The boards 3 are verticallystacked with the base frame 2. That is, the through-holes for thecontact elements 4 penetrate the three layers. In the illustratedexample, 14 through-holes for the contact elements 4 are formedvertically and 14 through-holes 4 are formed horizontally as shown inFIG. 2. In total, there are 196 through-holes 4 for the contactelements. The contact elements 5 (described later) are passed throughthe through-holes 4. The through-holes 4 in which the contact elements 5are inserted are exposed in the opening in the top surface of the baseframe 2 and in the opening in the bottom surface. The four corners aremounted together with the boards 3 (described later) with board-lockingpins 3 a, thus stacking the boards 3.

A plurality of mounting pins 6 for the printed circuit board protrudebelow the base frame 2 and are inserted in socket-holding holes formedin the printed circuit board (not shown). The pins 6 are forced to beinserted to their respective socket-holding holes.

The locking means 7 serve to hold the IC device therebetween, and aremounted at the central portions of the four sides between the cover 1and the base frame 2. Each locking means 7 comprises a lockinglever-fixing shaft 7 a and a locking lever 7 b pivotally mounted to thelocking lever-fixing shaft 7 a. This shaft 7 a extends horizontally inthe space between the cover 1 and the base frame 2. That is, verticalrotation is permitted. The kick spring 7 c, also called as hairspring,has a central winding portion that is wound from two to four timesaround the locking lever-fixing shaft 7 a described above. One side ofthe kick spring 7 c bears against the inner surface off the cover 1,while the other side bears against an arresting portion 7 e of thelocking lever 7. Resilience of the kick springs 7 c is imparted to thecover 1 and to the locking lever 7 b . Each kick spring 7 c may be madeof double structure.

The locking lever-pushing portion 7 d engaging with the inner lower endside 1 a of the aforementioned cover 1 is formed below the locking lever7 b to push the cover 1 downward, thus rotating the locking lever 7 bagainst the resilience of the kick springs 7 c. IC device-sandwichingportions 7 e are formed at the front ends of the locking levers 7 b tohold the substrate of the IC device from four directions therebetween,the substrate swelling like a jaw.

The numerous contact elements 5 are passed through the numerousthrough-holes 4 in the boards 3. Each contact element 5 has a contactelement center-winding portion 5 a fabricated by winding a single springwire into a coil. The center-winding portions 5 a of the elements areinserted in the contact element through-holes 4 formed in the base frame2. Contact element both side-winding portions 5 b are closely adhered toboth sides of the contact element center-winding portion 5 a and extendfrom the center-winding portion 5 a. Each contact element bothside-winding portion 5 b has spirally wound portions and a spacingwinding portion. The contact element both side-winding portions 5 b areinserted in the contact element through-holes formed in the boards 3,respectively, that are vertically stacked. Both-end portions of eachcontact element 5 protrude from the top and bottom surfaces of the topand bottom boards 3 through the contact element through-holes 4. Thatis, the contact elements 5 slightly protrude from the top and bottomsurfaces of the top and bottom boards 3.

The contact elements 5 are made of a spring wire fabricated fromberyllium copper, copper phosphate, or copper (i.e., copper or a copperalloy). The wire is surface-treated. For example, the wire is platedwith a metal such as gold, nickel, or aluminum. In the presentembodiment, the diameter of the spring wire is about 0.09 mm (±0.02 mm).The spring wire has electrical conductivity and resilience.

First, the spring wire is wound into a coil to fabricate the socketcenter-winding portion 5 a. The wire of the socket center-windingportion 5 a is wound tightly and so there is no elasticity. However, ithas flexibility owing to the resilience. Furthermore, adjacent coils ofthe spring wire are in contact with each other and electrical shortingoccurs in this section. A short conductive path is formed. In thepresent embodiment, the coils have an outside diameter of 0.48 mm (−0.02mm) and a length of 1.6 mm (±0.1 mm). They are inserted in the numerous(e.g., 196) contact element through-holes 4 in the boards 3.

Then, the socket both side-winding portions 5 b extend from both sidesof the socket center-winding portion 5 a and have diameters of about0.36 mm (±0.05 mm). An inner adhered winding portion, a spacing windingportion, an outer adhered winding portion, and a contact portion aresuccessively formed toward the outside in each of the socket bothside-winding portions 5 b. The socket center-winding portions 5 a areinserted in the contact element through-holes 4 formed in the center ofthe base frame 2. The socket both side-winding portions 5 b are insertedin the contact element through-holes 4 formed in the stacked boards 3,respectively, and the top portions of the contact elements 5 are made toprotrude.

That is, the inner adhered winding portions formed inside each of thesocket both side winding portions 5 b, extend from both sides of thesocket center winding portions 5 a and are closely wound at least onceinto a coil. The number of turns is calculated based on the weightapplied. In this structure, the wire is closely wound and so there isflexibility though there is no elasticity. Furthermore, the conductivepath is electrically shorted and short.

The spacing winding portions extend from the outside of the inneradhered winding portions and are wound into coils with spacing.Resilience imparts elasticity and flexibility. The elasticity takes upthe pressure produced when the printed circuit board is depressed.

The outside adhered winding portions extend outwardly from the spacingwinding portions, respectively, and are closely wound into coils atleast once in the same way as the aforementioned inner adhered windingportions. The number of turns is computed based on the weight appliedwhen the board is depressed. In this structure, the wire is closelywound and so there is flexibility though there is no elasticity.Furthermore, the conductive path is electrically shorted and short.

Their contact portions make contact with the contact portions of theterminals of the IC device that are at both ends of the IC device socketin accordance with the present invention. Furthermore, their contactportions make contact with the contact portions of the printed circuiton the printed circuit board. Their front ends are closed and wound.Their end portions are made horizontal to assure that they make contacteasily.

In the IC device socket using the contact elements 5 and built inaccordance with the present invention, the cover 1 is pushed downward tocause the inner lower end sides 1 a of the cover 1 to depress thelocking lever-pushing portions 7 d disposed in four directions at thesame time. The locking lever 7 b is rotated about the locking leverrotation shaft 7 a against the kick spring 7 c. The rotation increasesthe space between the IC device-sandwiching portions 7 e and theunderlying board 3. Then, the IC device is mounted, and the pushingforce applied from the cover 1 is relieved.

The pushing force applied from the cover 1 is relieved and thus thelocking lever 7 b holds the IC device between the boards 3 and the ICdevice-sandwiching portions 7 e by the resilience of the kick spring 7c. The locking lever makes contact with the contact portions of theterminals of the IC device and with the top ends of the contact elements5 of the IC device socket, thus making electrical connections.

A plurality of printed circuit board-mounting pins 6 protruding downwardfrom the base frame 2 are inserted and held in holding holes formed inthe printed circuit board (not shown). Thus, the pins make contact withthe lower ends of the contact elements 5 protruding from the bottomboard 3, thus making electrical connections.

INDUSTRIAL APPLICABILITY

In the present invention, the structure described above assures stableand reliable connections because of contact elements fabricated bywinding a spring wire into a coil, the contact elements beingelectrically connected with the contact portions of numerous terminalsof a leadless IC device and with the printed contact portions on aprinted circuit board. The cover of the socket is pushed downward torotate the locking levers that are disposed in four directions. Thisreleases the IC device-sandwiching portions and relieves the depression.Consequently, the IC device is held and electrical connections arefacilitated. In this way, the present invention is of great utility.

What is claimed is:
 1. A socket for a leadless IC device equipped with anumber of terminals having contact portions, said socket being adaptedto electrically connect the contact portions of said terminals of saidIC device with contact portions of a printed circuit on a printedcircuit board, said socket comprising: a boxlike cover having openingsin its top and bottom surfaces; boxlike base frame having openings inits top surface and bottom surfaces, said base frame having lower sidesthat can be withdrawably inserted via a coil spring into the openingformed in the bottom surface of said cover; a base frame-fixing framefor limiting sinking movement of-said base frame; a top board and abottom board stacked on said base frame; a number of through-holes forcontact elements extending through said boards and base frame; a numberof contact elements being inserted in said through-holes, respectively;fixing pins protruding downwardly from said base frame for mounting tosaid printed circuit board; locking means mounted between-said cover andbase frame to lock said IC device; said locking means having lockinglever rotating shafts extending horizontally, said locking leverrotating shafts being located in the central portions of four sides ofeach of said cover and base frame; locking levers pivotally mounted tosaid locking levers, respectively; kick springs wound around saidlocking lever rotating shafts, respectively, and having sides thereofengaging with said cover and locking levers, respectively; said lockinglevers having locking lever-pushing portions, respectively; said lockinglevers having IC device-sandwiching portions at their front ends; meansfor pushing said cover downwardly to cause inner corner portions thereofto push against the locking lever-pushing portions, respectively; eachof said contact elements having a contact element center-winding portionand contact element side-winding portions, said contact elementcenter-winding portion being fabricated by winding a spring wire closelyinto a coil, said contact element side-winding portions being in closecontact with both sides of said contact element center-winding portionand extending from said contact element center-winding portion, each ofsaid contact element both side-winding portions having spirally woundportions and a portion wound with spacing; and said contact elementseach having side portions protruding from and inserted into said contactelement through-holes formed in said contact elements.